A mooring in oceanography is a collection of devices, connected to a wire and anchored on the seabed/sea floor, lake bed, river bed, or bed of other waterway. Typically, the mooring is held up in the water column by a variety of subsurface or surface floatation devices (steel floats, glass floats, plastic floats, etc.), and held in place on the waterway bed with a heavy anchor. Devices attached to the mooring often comprise sensors of various types that are designed to measure various conditions or things found in the ocean. For example, the sensors could include devices such as current meters, conductivity/temperature/depth sensors, and other biological sensors.
Unfortunately, because of the impracticability of directly connecting these sensors to typical power generation plants, these sensors are very often powered via one or more batteries or battery packs, all of which have a limited lifespan once deployed. There is thus a significant cost to maintaining oceanographic moorings. For one, these batteries require periodic changing, some on relatively short intervals, such as every six or twelve months. To replace the batteries, a crew and vessel are required to travel to the mooring to replace the battery or battery pack. Vessel and crew costs can be extremely high. To minimize this cost and to achieve deployments of longer duration, electricity use may be minimized in order to try to prolong the lifespan of the battery or battery pack. One way of accomplishing this is to reduce the sampling rate of the sensors so as to lower their average power consumption and thereby reduce the amount of power drawn from the battery or battery pack. Naturally, this results in the sensors capturing less data over a given time period, which is not ideal for research or the like. If, however, real time data is desired or a necessity, because acoustic or inductive telemetry systems that allow for the capture and transmission of real time data require a lot of power, this drains the battery or battery pack quickly, thereby increasing maintenance costs for such applications.
There are a variety of known methods of providing power to traditional moorings, including two methods that are surface mounted. The first is solar based, drawing power from the sun through panels located at the water surface. The second is a wave power harvesting system, which generates power from ocean waves, again at the surface of the water. The latter type of systems are disclosed in, for example, U.S. Pat. No. 6,791,205 B2 (Woodbridge), U.S. Pat. No. 6,647,716 B2 (Boyd), and U.S. Pat. No. 7,535,117 B2 (Montgomery). The power in both the solar and wave powered cases is transmitted from the water's surface where it was generated down to instruments in the mooring through a power cable. However, because this distance can be considerable in a deep water mooring, a lengthy cable must be used at significant cost.
It is also known to convert the mechanical energy from subsurface ocean currents into electrical energy, and a great deal of effort has been expended commercially to develop large scale tidal turbine systems, including those for grid-tied applications. For example, U.S. Pat. No. 4,026,587 (Hultman and Hultman) discloses an underwater turbine to be mounted on a seabed by way of a large concrete base, upon which is rotatably mounted a large electric generator. However, such a system is not suitable for mounting on moorings to provide power to sensor systems. Indeed, there are few existing small-scale power generation systems for oceanographic applications, even though there is an ever increasing number of reasons for taking ocean measurements, and a greater need for small-scale power generation systems that can support sensor arrays to take these measurements. Historically, for example, most of the measurement programs being conducted in the ocean have been sponsored by governments and operated and managed by scientists and engineers from international ocean research institutions and scientific agencies. There have also been a number of specialized ocean measurement programs that have been sponsored and carried out by the navies of the world for defense-related purposes. Today, however, there are a substantial and ever increasing number of commercial organizations that are starting to appreciate the need to collect and analyze information, including real-time information, about the physical, chemical, and biological processes that are occurring in various undersea locations around the world. Whether it be for the advancement of pure science, for health and human safety reasons, for military protection purposes, or for commercial exploitation, ocean observation and measurement is an emerging and growing market.
It would be desirable to employ a small-scale subsurface power generation system that can augment traditional oceanographic mooring designs by harvesting power from ocean currents and providing it to sensors in the mooring itself, with the potential benefits of allowing the sensors to operate and be powered for longer periods of time (i.e. increased deployment duration), whether in shallow or deep water, while maintaining or increasing the amount of data that may be captured as a result thereof (including the option of real-time data collection), as well as reducing maintenance costs.
It would further be desirable to use such a subsurface power generation system with traditional oceanographic moorings and their associated sensors in order to extend the lifespan and/or increase the usability of these moorings and sensors by allowing them to be recycled or re-used, thereby avoiding or minimizing replacement and upgrade costs.